Kavli Affiliate: Roger W. Romani
| First 5 Authors: Andrew G. Sullivan, Roger W. Romani, , ,
| Summary:
PSR J2215+5135 (J2215) is a `redback’ spider pulsar, where the intrabinary
shock (IBS) wraps around the pulsar rather than the stellar-mass companion.
Spider orbital light curves are modulated, dominated by their binary companion
thermal emission in the optical bands and by IBS synchrotron emission in the
X-rays. We report on new XMM-Newton X-ray and U-band observations of J2215. We
produce orbital light curves and use them to model the system properties. Our
best-fit optical light model gives a neutron star mass $M_{NS}=1.98pm0.08$
M$_odot$, lower than previously reported. However, uncertainty in the stellar
atmosphere metallicity, a parameter to which J2215 is unusually sensitive,
requires us to consider an acceptable systematic plus statistical range of
$M_{NS}sim1.85-2.3$ M$_odot$. From the X-ray analysis, we find that the IBS
wraps around the pulsar, but with a pulsar wind to companion wind momentum
ratio unusually close to unity, implying a flatter IBS geometry than seen in
other spiders. Estimating the companion wind momentum and speed from the X-ray
light curve, we find a companion mass-loss rate of ${dot M}_cgtrsim10^{-10}$
M$_odot$ yr$^{-1}$, so that J2215 may become an isolated millisecond pulsar in
$sim 1$ Gyr. Our X-ray analyses place constraints on the magnetization and
particle density of the pulsar wind and support models of magnetic reconnection
and particle acceleration in the highly magnetized relativistic IBS.
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